Single-Photon Generation from Stored Excitation in an Atomic Ensemble
Abstract
Single photons are generated from an ensemble of cold Cs atoms via the protocol of Duan et al. [Nature \textbf{414}, 413 (2001)]. Conditioned upon an initial detection from field 1 at 852 nm, a photon in field 2 at 894 nm is produced in a controlled fashion from excitation stored within the atomic ensemble. The single-quantum character of the field 2 is demonstrated by the violation of a Cauchy-Schwarz inequality, namely
w(
1
2
,
1
2
|
1
1
)=0.24±0.05≱1
, where
w(
1
2
,
1
2
|
1
1
)
describes detection of two events
(
1
2
,
1
2
)
conditioned upon an initial detection
1
1
, with
w→0
for single photons.